1. Field of the Invention
The present invention relates generally to the storage and transfer of substrates typically used in the fabrication of electronic devices such as integrated circuits and flat panel displays. Specifically, the invention relates to a load-lock chamber and a pre-processing or post-processing storage rack used to transition substrates from one environment to another environment in a processing system.
2. Background of the Invention
Vacuum processing systems used in the fabrication of integrated circuits and flat panel displays are generally known. An example of a vacuum processing system 100 is shown in FIGS. 1 and 2. The vacuum processing system 100 typically has a centralized transfer chamber 102 mounted on a monolith platform or main frame structure 110. One or more process chambers 106 are in communication with the transfer chamber 102 via access ports 105 and associated slit valves 107. Substrates are passed through the system by a substrate handling robot 103 disposed in the transfer chamber 102. The slit valves 107 isolate the process chambers 106 from each other and from the transfer chamber 102 while substrates are being processed. The transfer chamber 102 is typically held at a constant vacuum, while the process chambers 106 may be pumped to a greater or lesser vacuum than the transfer chamber 102 for performance of their respective processes. Afterward, the process chamber pressure returns to the level in the transfer chamber 102 before opening the slit valve 107 is opened to permit access between the chambers.
The substrate handling robot 103 disposed in transfer chamber 102 typically retrieves one or more unprocessed substrates from one or more load-lock chambers 112 connected to the transfer chamber 102 and places the substrates in the process chambers 106. The load-lock chambers 112 selectively cycle between the pressure level of the ambient environment and the pressure level in the transfer chamber 102 to transition the substrates between atmospheric pressure and the vacuum environment of the transfer chamber 102. The load-lock chambers 112 typically have a large volume and store multiple substrates. Typically, twelve to twenty-four substrates are stacked vertically in one or more substrate cassettes 109 disposed in load-lock chambers 112. The substrate cassettes 109 typically include a plurality of substrate supports spaced vertically to permit a substrate handling robot blade 115 to reach under a substrate to remove or place a substrate. Substrates are typically loaded in and removed from the load-lock chamber 112 by either a staging robot 113 (shown in FIGS. 1 and 3), or an operator at or near a frontend staging area 104.
Typically, the front-end staging area 104 is maintained at or near ambient or atmospheric pressure. Accordingly, prior to transfer of substrates into or out of the loadlock chamber 112, the atmospheric volume within the load-lock chamber 112 must be vented to atmospheric pressure before opening the valves of the load-lock chamber 112. Similarly, before transfer of substrates between the load-lock chamber 112 and the transfer chamber 102, the atmospheric volume within the load-lock chamber 112 must be evacuated to the low pressure maintained in the transfer chamber 102. Because of the sizable volume within typical load-lock chambers 112, a relatively lengthy amount of time is required to vent and then evacuate the load-lock chamber 112 before permitting access to the substrates by the substrate handling robot 103 This process may typically take approximately four (4) minutes to complete. During this time, the vacuum processing system 100 typically sits idle while awaiting the introduction of additional unprocessed substrates into the system.
It has been found that substantial production gains can be made by reducing the atmospheric volume within the load-lock chamber 112 serving the transfer chamber 102. Accordingly, systems having single substrate load-lock chambers have been developed to reduce venting and evacuation time within the load-lock process chamber 112, which has resulted in a reduction of process chamber idle time and an increase in production. One exemplary system of this type is shown in U.S. patent application Ser. No. 08/990,396, entitled xe2x80x9cSingle Wafer Load-lock Chamber For Pre-Processing And Post-Processing Wafers In A Vacuum Processing System,xe2x80x9d filed on Feb. 15, 1997, which is incorporated herein by reference.
However, the reduction in the number of substrates housed in the load-lock chamber 112 requires that the substrates must be transferred quickly into and out of the load-lock chamber 112. This can be problematic when substrates must be pre-heated prior to processing or cooled following processing before being replaced into a substrate cassette 109. Unfortunately, a shorter transition time through the load-lock chamber 112 may prevent the load-lock chamber 112 from sufficiently pre-heating a substrate prior to processing or cooling a substrate following processing.
To accommodate this cooling and/or pre-heating process, existing systems have provided cooling and/or pre-heating chambers attached to the transfer chamber 102. Because space may be limited on a typical transfer chamber 102, such systems are required to forfeit a facet on which a processing chamber 106 could be mounted. Alternatively, systems may have limited throughput due to a limited number of preheating/cooling chambers mounted to the transfer chamber 102 and/or the amount of time required to perform the pre-processing/post processing procedures. In systems where heating and/or cooling members are integrated within the load-lock chamber 112, throughput may be limited because a cooling process may require an extended cooling time beyond the time in which the substrate handling robot 103 can return to the load-lock chamber 112 to return a processed substrate or retrieve an unprocessed substrate for further processing. As a result, the system substrate transfer system is limited by the time required for the cooling process to be performed.
Accordingly, there is a need for a vacuum processing system that provides high throughput and pre-processing and/or post-processing processes. More particularly, there is a need for an integrated system having a load-lock chamber with an integrated staging, or storage rack mounted external to the transfer chamber for pre-processing and/or post-processing of substrates.
The present invention generally provides a vacuum apparatus for processing substrates, comprising a transfer chamber; one or more processing chambers in communication with the transfer chamber; a substrate handling robot disposed in the transfer chamber; and at least one load-lock chamber connected to the transfer chamber, with the load-lock chamber having one or more substrate support members for supporting one or more substrates. The apparatus preferably includes a substrate staging area and may further include a staging robot disposed in the staging area to load substrates into and remove substrates from the load-lock chamber.
In another aspect of the invention, the staging area may include one or more storage racks associated with the load-lock chamber for receiving and temporarily storing substrates. Further, the storage racks, preferably include at least a cooling element and are adapted to temporarily receive and cool substrates retrieved from the load-lock chamber following processing.
In another aspect of the invention, at least one of the storage racks may include a heating element adapted to pre-heat unprocessed substrates retrieved from the substrate cassette prior to processing. Further, the storage racks may include a cooling element and/or a heating element, each adapted to receive and process a substrate prior to transfer. Still further, the load-lock chamber may include a heating element disposed in connection therewith for pre-heating unprocessed substrates in the load-lock chamber, and the load-lock chamber may include a substrate support member for receiving a substrate thereon.
In another aspect of the invention, the load-lock chamber may include a substrate support member for receiving a single stack of two or more substrates thereon, preferably in a single load-lock chamber connected to a single facet of the transfer chamber. Further, each load-lock chamber may include a dual substrate support member for receiving two stacks of two substrates thereon. In another aspect, a plurality of load-lock chambers may be provided, wherein each load-lock chamber is connected to a different facet of the transfer chamber.
In another aspect, the invention is directed to a method of processing substrates, comprising the steps of providing unprocessed substrates to a load-lock chamber with a staging robot, retrieving the unprocessed substrates from the load-lock chamber with a substrate handling robot located within a transfer chamber, processing the unprocessed substrates in one or more process chambers connected to the transfer chamber, returning the processed substrates to the load-lock chamber with the substrate handling robot, retrieving the processed substrates from the load-lock chamber with the staging robot, placing the processed substrates in a cooling station located external to the load-lock chamber and the transfer chamber, and cooling the substrate in the cooling station; and retrieving the cooled substrates from the cooling station with the staging robot and placing them in a substrate cassette.
In another aspect, the invention is directed to a method of processing substrates, comprising: a) providing a vacuum apparatus with a transfer chamber, one or more processing chambers connected to the transfer chamber, a substrate handling robot disposed in the transfer chamber, and a load-lock chamber connected to the transfer chamber and having at least one substrate support member for supporting a substrate thereon; b) initially loading the load-lock chamber and transfer chamber with one or more unprocessed substrates; c) processing the substrates in one or more processing chambers; d) removing the processed substrates from the one or more processing chambers with a substrate handling robot; e) placing the processed substrates within the load-lock chamber with the substrate handling robot; f) retrieving the processed substrates within the load-lock chamber with a staging robot located external to the load-lock chamber; g) placing the processed substrates within a storage rack located external to the load-lock chamber with the staging robot; and h) repeating steps c) through g), while retrieving cooled substrates from the staging or storage rack with the staging robot and placing the cooled substrates within substrate cassettes with the staging robot during staging robot idle time.
Further, each substrate set may include a single substrate in each of two substrate stacks, and the method may further include the step of pre-heating the unprocessed set of substrates within the load-lock chamber prior to removal by the substrate handling member. Further, the method may include the step of pre-heating the unprocessed set of substrates within the storage rack prior to their placement in the load-lock chamber.
In still another aspect, the invention is directed to a staging module for use with a substrate processing system, comprising: at least one load-lock chamber adapted to be connected to a transfer chamber of the substrate processing system; and one or more storage racks associated with the load-lock chamber for receiving and temporarily storing substrates. At least one of the one or more storage racks may be a cooling rack, preferably including a cooling element, adapted to cool processed substrates following processing by the substrate processing system. Further, at least one of the one or more storage racks may be a pre-heating rack, preferably including a pre-heating element, adapted to pre-heat unprocessed substrates prior to processing by the substrate processing system. Still further, the staging module may include one or more cooling racks, preferably including a cooling element and one or more heating racks, preferably including a heating element.